Non-tubular type recycle system of wet bench tank

Details Non-tubular type recycle system of wet bench tank Non-tubular type recycle system of wet bench tank

2001-07-16

2003-04-22

Gulakowski, Randy (Department: 1746)

Cleaning and liquid contact with solids

Processes

Including regeneration, purification, recovery or separation...

C134S105000, C134S111000, C134S184000, C134S196000, C134S902000

Reexamination Certificate

active

06551412

ABSTRACT:

BACKGROUND OF THE INVENTION
In the semiconductor industry, wet benches are utilized in many applications, such as photoresist stripping, silicon nitride removal, and silicon oxide removal, for example. Wet etch processes are characterized by high selectivity and isotropy.
The common hardware setting for wet benches is a series of tanks which have various functions, such as a main etch process tank, an intermediary washer tank, a rinse tank, a dryer tank, etc. As shown in
FIG. 1
, in a conventional wet bench recycling system, the main etch process tank
10
can generally be simplified as: an outer tank (recycle tank)
10
housing an inner tank (process tank)
12
, a recycle tube
14
connecting the bottom of the outer tank
10
, as at
15
, to a pump
16
, filter
18
, heater
20
, etc., and back to the. bottom of the inner tank
12
, as at
21
, so that fluid
22
in the outer tank
10
is pumped by the pump
16
through a filter
18
, a heater
20
, etc., and then into the bottom
21
of the inner tank
12
so that fluid
22
from the inner tank
12
overflows, as at
24
, over the top of the inner tank
12
into the outer tank
10
. Thus the fluid
22
, such a chemical solvents, is recycled and used for additional runs.
However, some chemical solvents in wet processes are very viscous, i.e. thick and slow flowing, and get more so after series of runs. This causes undesirable “reaction incomplete” issues.
Chemical solvent reaction rates (&ggr;) is generally related to temperature (T), the concentration gradient between the chemical solvent and etched film (&Dgr;C), and the turbulence (mixing) of flow (&phgr;), i.e.:
&ggr;=
fn
(
T, &Dgr;C, &phgr;
)
Temperature (T), in most cases, is optimized and restricted by process limitations and can not be modified arbitrarily. The concentration gradient (&Dgr;C) can be obtained by supplementing new chemical solvent
22
frequently, however this sharply increases cost and is not economical. Unfortunately, the third key element of the chemical solvent reaction rate, the turbulence (mixing) of flow (&phgr;), usually performs poorly because of the high viscosity of some of the wet process chemical solvents
22
, and also due to the current hardware design as shown in FIG.
1
.
Viscous liquid moving within tubes will form laminar flow and the average velocity (&ugr;) can be calculated by the formula:
&ugr;=(&Dgr;
P
)(square
D
)/(32)(&mgr;)(&Dgr;
L
)
where:
&ugr;: the average velocity, m/s;
&Dgr;P: the driving pressure, N/square (m);
D: the inner diameter of the tube, m;
&mgr;: the viscosity of solvent, (N)(s/square (m))
&Dgr;L: the equivalent tube length, m.
Therefore, the recycle flow rate would be extremely low due to the high viscosity (&mgr;) of the solvent
22
and the equivalent tube length (&Dgr;L) so that the circulation and etching rate in the inner tank
12
will be poor.
Besides, the filters
18
are often seriously jammed by jelly-like remnants that reduce the driving pressure (&Dgr;P) after a few runs. To remedy this problem, either the chemical solvents
22
must be frequently renewed or the filters
18
must be frequently replaced.
U.S. Pat. No. 4,917,123 to McConnell et al describes a wafer treatment system including a recycle system.
U.S. Pat. No. 5,632,866 to Grant describes a point-of-use recycling of wafer cleaning substances.
U.S. Pat. No. 5,409,310 to Owczarz describes a semiconductor fluid blending system including a recycle.
U.S. Pat. No. 5,885,403 to Cheng describes a system for cleaning and etching a wafer that a buffer tank that stores a unique chemical solution, a loader for loading the wafer, and at least one process tank for retaining the loaded wafer. The process tank being coupled to the buffer tank to receive the chemical solution from the buffer tank and to perform the cleaning and etching of the wafer.
SUMMARY OF THE INVENTION
Accordingly, it is an object of one or more embodiments of the present invention to provide a wet bench recycle system usable with viscous chemical solvents.
Another object of one or more embodiments of the present invention is to provide a viscous chemical solvent wet bench recycle system that does not necessitate frequent changing of the chemical solvent.
Yet another object of one or more embodiments of the present invention is to provide a viscous chemical solvent wet bench recycle system that does not necessitate frequent changing of filters.
A further object of one or more embodiments of the present invention is to provide a viscous chemical solvent wet bench recycle system that has superior tank circulation compared to prior such systems.
Another object of one or more embodiments of the present invention is to provide a viscous chemical solvent wet bench recycle system that is easier to clean and maintain than conventional viscous chemical solvent wet bench tube recycle systems.
Another object of one or more embodiments of the present invention is to provide a viscous chemical solvent wet bench recycle system that has prolongs the chemical solvent and filter life cycles, gaining available system up-time.
Another object of one or more embodiments of the present invention is to provide a viscous chemical solvent wet bench recycle system that reduces process time, and gains throughput.
Other objects will appear hereinafter.
It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, an outer recycle tank is provided having sides and a bottom. The outer recycle tank holding outer recycle tank fluid. An inner process tank is provided having sides and a sieved bottom housed within the outer recycle tank. The inner process tank sides being spaced apart from the sides of the outer recycle tank sides and the inner process tank bottom being spaced apart from the outer recycle tank bottom. The inner process tank holding inner process tank Fluid. A wide area filter fitted within the inner process tank proximate the inner process tank sieved bottom is provided. A vertically moveable top cover is provided at an uppermost position and fitted between the inner process tank sides and the outer recycle tank sides. The top cover having one-way valves therein that permit flow of fluid only downward through the one-way valves. The vertically moveable top cover having a top and a bottom. A downward force means is provided to vertically depress the moveable top cover downward, forcing a portion of the outer recycle tank fluid through the inner process tank sieved bottom and the wide area filter whereby a portion the inner process tank fluid is forced upwardly and over the inner process tank sides and onto the top of the top cover, and whereby passage of the outer recycle tank fluid through the wide area filter recycles the outer recycle tank fluid. An upward force means is provided to then vertically raise the moveable top cover back to the top cover uppermost position, whereby the inner process tank fluid on top of the top cover passes downward through the top cover one-way valves.


REFERENCES:
patent: 4917123 (1990-04-01), McConnell et al.
patent: 5393347 (1995-02-01), Miranda
patent: 5409310 (1995-04-01), Owczarz
patent: 5632866 (1997-05-01), Grant
patent: 5873381 (1999-02-01), Han
patent: 5885403 (1999-03-01), Cheng
patent: 5922138 (1999-07-01), Shindo et al.
patent: 6199564 (2001-03-01), Yokomizo
patent: 6199568 (2001-03-01), Arai et al.
patent: 6357458 (2002-03-01), Tanaka et al.

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